Jean Piaget

The most influential developmental psychologist in the history of psychology is the infamous Jean Piaget! His early works began with the close observation of his own three children. Piaget explored the how and why of mental abilities and how they change over time. He believed that development depends on a large part of the child's manipulation of and the active interaction with the environment, all while believing knowledge comes from action. From these beliefs comes Piaget's theory of cognitive development.

Cognitive Development
Cognitive development refers to the gradual, orderly changes by which mental processes become more complex and sophisticated. Paiget's theory of cognitive development proposes that a child's intellect, or cognitive abilities, progresses through four distinct stages. Each of the four stages is characterized by the development of new abilities and ways of processing information.

How does development occur?
According to Piaget, development occurs through schemes, and assimilation and accommodation. Schemes are those mental patterns that guide behavior.

We use schemes to find out about and act in the world. For example, when young infants discover that an object with make a noise when banging it against something, that observation tells them about that object. Young infants will also make discoveries with objects by biting them, sucking on them, or throwing them. Each of these approaches to interacting with the objects is a scheme.












video portraying a pouring schema
We are able to adjust our schemes in response to the environment through assimilation and accommodation, and this process is referred to as adaptation. Assimilation is the process of understanding a new object or event in terms of an existing scheme. For example, when young infants are discovering small objects they have never seen before but resemble familiar objects, they are likely to use the existing schemes to explore the object, such as banging it against something, biting it, sucking on it, or throwing the object. Accommodation is the process of modifying an existing scheme when faced with new information or a new experience. Therefore, for example, if a young infant is given an egg for the first time, the young infant will use the existing schemes the first time, but once he/she discovers that when the egg is thrown or banged against something it will break, then the infant will adjust their schemes when dealing with new objects in the future by banging them hard or soft.


















When we are faced with situations that could not be addressed using existing schemes, this creates an imbalance between what is understood and what is encountered, which is referred to as disequilibrium. In order to adapt to the disequilibrium, people naturally try to reduce the imbalance by developing new schemes or adjust existing ones until equilibrium is reached. This process of restoring balance is called equilibration, and Piaget believed learning depends on this process.


A prime opportunity for children to learn and grow occurs when equilibrium is upset. As a result, new ways of thinking emerge and the children advance to a new stage of development. Equally important are the physical experiences and manipulation of the environment, which also help children learn and grow.

Stages of Development
Piaget divided the cognitive development of children into four stages: sensorimotor, preoperational, concrete operational, and formal operational. His belief was that all children pass through each stage and no child can continue onto the next stage without first completing the preceding stage. However, children pass through these stages at different rates. Each stage is marked by new intellectual abilities that allow individuals to understand the world in a more complex fashion.

Sensorimotor (birth to age 2)This stage is the earliest stage of development. It is referred to as the sensorimotor stage because during this stage babies and young children explore their world by using their senses and their motor skills. Dramatic changes occur as infants progress during the sensorimotor period. Initially, infants have inborn behaviors called reflexes. These are automatic responses to stimuli, such as an eye blinking in response to bright light. These are the building blocks from which the infant's first schemes are formed. Infants begin to use these reflexes to produce more interesting and intentional patterns of behavior. This type of learning occurs initially through accident and then becomes more intentional trial and error efforts. By the end of this stage, Piaget believed children have progressed from earlier trial and error approaches to a more planned approach to problem solving. Thinking begins to appear at this stage as well. It means that a child can think through and plan behavior. Another important aspect of the sensorimotor period is the development of object permanence. This refers to the fact that an object exists even if it is out of sight. Piaget argued that children must learn that objects are physically stable and exist even when the objects are not in the child's physical presence. When children develop this way of thinking, they have taken a step toward more advanced thinking.
Preoperational (ages 2 to 7)During this stage, children's language and concepts develop at a rather fast pace, yet much of their thinking is still primitive. A child at this stage is only able to focus on one aspect at a time, and ignores all others. Piaget referred to this as the principle of conservation, which is the concept that certain properties of an object remain the same regardless of changes in other properties. For example, if an adult were to pour milk from a tall, narrow container into a shallow, wide one in the presence of a preoperational child, the child will firmly believe the tall glass has more milk. Several aspects help to explain the error on conservation. First is centration, which means paying attention to only one aspect of an object or situation. Next is reversibility, which is the ability to perform a mental operation and then reverse one's thinking to return to the starting point. The thinking of children at this stage can be characterized as being irreversible. Another aspect to explain the error on conservation is in the focus on states. Children are only able to focus on the beginning and end state, and forget what occurs between the two. Finally, children in this stage are egocentric, meaning that they believe everyone views the world as you do. Children are unable to take the perspectives of others and often interpret events entirely in reference to themselves.
Concrete Operational (ages 7 to 11)Children at this stage of development can form concepts, see relationships, and solve problems, but only as long as they involve objects and situations that are familiar. They are still unable to think like adults and are have difficulty with abstract thought. These children no longer have difficulty with conservation problems because they have developed the concept of reversibility. In addition, these children are also able to respond to inferred reality, which is seeing things in the context of other meanings. An important task children are able to acquire during this stage is seriation. This refers to arranging things in a logical progression. In order to do this, children must be able to order or classify objects according to some criteria or dimension. Once this skill is mastered, children are then able to acquire transivity, which is the ability to infer a relationship between two objects on the basis of knowledge of their respective relationships with a third object. By the end of this stage, children have the mental abilities to learn how to add, subtract, multiply, and divide. One other important aspect of the concrete operational stage is the fact that children are moving from egocentric thinking to decentered or objective thought. This allows children to see that others can have different perceptions than they do. One final ability of those children in this stage is the acquisition of class inclusion. This refers to a skill that allows individuals to think simultaneously about a whole class of objects and about relationships among its subordinate classes.
Formal Operational (age 11 to adulthood)Within this stage comes the ability to deal with potential or hypothetical situations--a more abstract way of thinking. Children within this stage are able to monitor, or think about, their own thinking. An ability that Piaget recognized in young adolescents is the ability to reason about situations and conditions that have not been experienced. Adolescents are not bound by their own experiences of reality, so they are able to apply logic to any given set of conditions.


It's said that Piaget's theory still dominates the study of human development!